Brother Facsimile Equipment MFC7420 - Manual (Page 225)

Confidential 9-37
I-12 Poor fixing
Possible cause Step Check Result Remedy
Print paper 1 Is thick paper of more than
43lb being used? Yes Recommend to use the specified
types of paper.
Toner sensor
failure
(When
printing is
faint.) 2 Is the problem solved by
replacing the drum unit or
the toner cartridge? Yes 1) Toner is empty.
2) The toner sensor is defective.
Clean the toner sensor.
3) If the wiper in the toner
cartridge is broken, replace the
toner cartridge with a new one.
Fixing unit
thermistor
failure 3 Is the thermistor fitted
correctly? No Fit the thermistor correctly.
Low-voltage
power supply
PCB failure 4 Is the problem solved by
replacing the low-voltage
power supply PCB? Yes Replace the low-voltage power
supply PCB.